World's Fastest Man

Usain Bolt is a phenomenal athlete. He’s the fastest man in the World. He’s the fastest person who has ever lived (according to all records we have).

He currently holds the World Record for the 100m sprint at just 9.58 seconds (achieved in Berlin in 2009, beating his own previous record of 9.69 seconds at the 2008 Olympic Games in Beijing).

Running 100m

Remember back to high school Physics?

Recalling back that speed = distance / time, we can work out Usain’s speed during this race, right?

If he covered the 100m in 9.58 seconds, that’s a speed of 100/9.58 = 10.44 m/s (which is 23.35 mph), right?

Well, sort of …

23.35 mph is certainly Usain’s average speed over the race, but as you can appreciate, he does not run at this rate for the entire race.

Usain starts at rest, so he has to accelerate to build up his speed. He does not instantly start to run at 23.35 mph out of the blocks!

Also, there is his reaction time. After the gun fires, even the most alert, focused and dynamic individual needs time to hear, process, and react. Even with fighter pilot reflexes there is a delay from when the race starts until the body can respond.

Both these above facts mean that Usain will need to run, at times, faster than 23.35 mph to create this average speed.

Just what does a top sprinter's speed profile look like …

Distribution of Speed

Segment (m)

Time (s)

0-10

1.85

10-20

1.02

20-30

0.91

30-40

0.87

40-50

0.85

50-60

0.82

60-70

0.82

70-80

0.82

80-90

0.83

90-100

0.90

To the left is a table of split times for Usain’s Olympic Gold Medal race in the 2008 Beijing Olympics [Data courtesy SpeedEndurance.com].

The time required to travel each 10m section is shown (in seconds).

This data was obtained from analysis, frame-by-frame, of high speed video recorded at the event.

Here is the data plotted as a histogram:

As you can see, the first 10m of the race takes over twice as long as a 10m segment in the middle of the race. It is in this first section that Usain is reacting to the starting gun and then accelerating his body to warp speed.

Each subsequent 10m section (up until 80% of the race) is covered at a faster and faster pace as Usain really gets into his stride.

Finally, in the last 20m, there is a slight reduction in speed (the segments taking a little longer). This is Usain backing off slightly once he is assured of the victory. If you look at the video of his victory you can see that he even slows down enough to give a slight victory celebration.

Segment

Time (s)

Speed (ms-1)

Speed (mph)

0-10

1.85

5.41

12.09

10-20

1.02

9.80

21.93

20-30

0.91

10.99

24.58

30-40

0.87

11.49

25.71

40-50

0.85

11.76

26.32

50-60

0.82

12.20

27.28

60-70

0.82

12.20

27.28

70-80

0.82

12.20

27.28

80-90

0.83

12.05

26.95

90-100

0.90

11.11

24.85

The table on the left shows the average speed calculated over each 10m segment. The speed is show in both m/s (for my Metric friends), and in MPH (for everyone else).

You can see in the middle of the race how Usain achieved a speed of over 27 mph!

Below is a graph of this speed data. You can see the acceleration, the build up of speed to a plateau, followed by the slight fall-off at the end of the race.

Theoretical Max

What is the theoretical shortest time that Usain could cover a 100m course?

As we can see, the things that drag his transit time down are the start of the race (reaction time and acceleration region), and at the end of the race, during his (well deserved) showboating!

What if we removed these restrictions and started the timing based on a rolling start? Just like NASCAR; we let Usain start running, get up to speed, and only then pass the start line. If we encouraged him to carry on running through the finish line without slowing down (like running through First Base in baseball), what would the time be?

Looking at the above speed curve, if we say that Usain as 'at speed' when he reaches a velocity of 11.5 m/s, we can give him a lead-in acceleration lane of about 30m. Assuming he had a good breakfast and can keep this speed up over the entire course, (maybe we trick him and put a 'fake' finish line 20m beyond where we really stop timing him to encourage him to keep on running!) He could, theoretcally, cover 100m in approx 8.7 seconds!

(This running start idea is not quite as contrived as it sounds. This is what happens in the relay race.)

Move over Usain

Usain may be insanely fast, but he’s not the fastest animal on the land.

That honor goes to the Cheetah (Acinonyx jubatus), a large feline found in Africa and Asia. These endangered cats have been clocked at over 75 mph (and have been recorded as accelerating from 0-100 kph (62 mph) in under three seconds; that’s Bugatti Veyron territory).

So a cheetah can out-pace Usain, but if he had a head-start, Usain could probably out-run the animal. After a couple of hundred yards the cheetah will run out of steam. With a sufficient head start, Usain could get a way … probably …

For more fascinating animal speed facts, go here. For instance, did you know that an Ostrich can jog at over 30 mph for over half an hour? Or that a Peregrine Falcon can achieve speeds in excess of 240 mph in a dive?